The III does not have factory leather, so you're asking about either a dealer installed or port option, and it can vary. Cost varies, too. Best to ask a dealer where you'll buy. On the IV the door panels are finished in what I expect is a nice soft-touch vinyl, but I doubt they use the leather on the door. Just the seating area is listed in the Toyota specs, unless somebody has a way to test a door panel for leather versus vinyl.
The issue will never go away. Both sides like what they like. If your body oozes oils ... if you put dogs in the car ... if slobs spill their coffee ... if the new-born vomits up that curdled milk ... good luck with the cloth. .
